Physical Sciences and Mathematics Commons^™

Characterizing Agn Influence On The Calculated Metallicities Of Adjacent Star-Forming Spaxels, Aidan Khelil

Honors Papers

In this thesis, I introduce a method to identify and characterize the effects of active galactic nuclei (AGN) on the spectra of nearby star-forming regions. I analyze spatially-resolved areas of galaxies called “spaxels” within Data Release 15 of the Sloan Digital Sky Survey (SDSS) with the goal of locating those which are physically close to AGN. I find those spaxels with calculated metallicities which lie adjacent to AGN-flagged spaxels and characterize their metallicity values relative to the spaxels which are not adjacent to AGN-flagged spaxels, using a total of 11 separate metallicity calibrations. I find that the current methods to …

Energy And Greenhouse Gas Savings For Leed-Certified U.S. Office Buildings Using Weighted Regression, Tian Liang

Honors Papers

In this study, we studied the energy consumption and greenhouse gas emission performance of LEED-certified office buildings. We obtained the 2016 energy consumption and greenhouse gas emission data for 4002 office buildings from nine major US cities, including 522 buildings that we identified as LEED-certified. We discovered that LEED buildings used significantly more electricity percentagewise as their energy source. We also discovered that the locations and ages of buildings have significant effect on their performance. We removed the effect of locations and building ages using weighted regression. Our result showed that LEED office buildings used 11% less site energy, 9% …

A Gas Flow-Through System For Hydrogen Isotopic Separation With Metal-Organic Frameworks, Katharine Harp Rigdon

Honors Papers

In this thesis, we designed and built a gas flow-through system to study dynamic adsorption separation of hydrogen isotopes in metal-organic frameworks (MOFs). MOFs are porous, crystalline materials composed of metal complexes connected by organic linkers. They have been proposed as a cheaper, more energy efficient approach to hydrogen isotope separation than current industrial methods. We have previously found evidence of a zero-point energy-based separation mechanism for hydrogen isotopes in two MOFs: Co-MOF-74 and Cu(I)-MFU-4l. This mechanism, chemical affinity quantum sieving (CAQS), has been extensively studied under static equilibrium conditions. The system in this work was developed so that CAQS …

Testing The Production Of Scintillation Arcs With The Pulsar B1133+16, Stella Koch Ocker

Honors Papers

Pulsars are extremely dense, highly magnetized stars that emit pulses of radio emission every millisecond or so. The arrival times of their radio signals at Earth observatories can be used as a clock precise enough to detect gravitational waves. Performing such a detection requires the mitigation of interference effects from the interstellar medium: the slightly ionized, mostly hydrogen gas that the radio waves traverse as they travel from the pulsar to Earth. We investigate radio wave delays using a powerful tool: scintillation arcs, fluctuations in frequency and time of the pulsar signal intensity that are manifested as parabolic arcs in …

Simulating Pulsar Signal Scattering In The Interstellar Medium With Two Distinct Scattering Phenomena, Adam P. Jussila

Honors Papers

In this thesis, I discuss the creation of a simulation that attempts to reconstruct secondary spectra of pulsars by simulating the scattering in the interstellar medium. For the simulation, we focus on two distinct scattering phenomena, namely a coherent deflection at grazing incidence along a sheet of material, and a random deflection due to a random-walk type process through clouds of material. The simulation focuses on a representation known as a Wavefield Representation that our group has not utilized to this extent before, and it allowed us to understand the physics behind these scattering events in new depths. The final …

Hydrogen Isotope Separation In Metal-Organic Frameworks, Naiyuan Zhang

Honors Papers

In this thesis we present our research on hydrogen isotope separation using metal-organic frameworks (MOFs). Deuterium is one of the two stable isotopes of hydrogen. Despite its wide range of application, currently there is no ideal industrial method that can separate deuterium in a fast and efficient fashion. MOFs are a class of porous materials consisting of metal ions or clusters connected by organic ligands. They have shown great potential in separating hydrogen isotopes via quantum sieving effect. In this thesis, we first provide background on two state-of-art MOFs, Co-MOF-74 and Cu(I)-MFU-4l. Then we elaborate on the statistical theory of …

Infrared And Thermal-Desorption Spectroscopy Of H2 And D2 In Metal Organic Frameworks, Kai Shinbrough

Honors Papers

In this thesis we provide an introduction to the use of Metal-Organic Frameworks (MOFs) for hydrogen storage and for the separation of hydrogen isotopologues, H2 and D2. MOFs are a class of materials comprised of `building-block’ metal-oxide clusters connected by organic ligands, which have the capacity to adsorb molecules such as hydrogen through weak, physisorptive mechanisms. We provide some background on the quantum mechanical structure of hydrogen isotopologues, the structure of a few state-of-the-art MOFs, the quantum mechanics of infrared spectroscopy, and the desorption dynamics of adsorbates generally. We provide a description of the experimental apparatus and procedure used in …

Improving The Sensitivity Of A Pulsar Timing Array: Correcting For Interstellar Scattering Delays, Jacob E. Turner

Honors Papers

The NANOGrav collaboration aims to detect low frequency gravitational waves by measuring the arrival times of radio signals from pulsars. A confirmation of such a gravitational wave signal requires timing tens of pulsars with a precision of better than 100 nanoseconds for around 10 – 25 years. A crucial component of the success of pulsar timing relies on understanding how the interstellar medium affects timing accuracy. Current pulsar timing models account only for the large-scale dispersion delays from the ISM. As a result, the relatively small-scale propagation effects caused by scattering are partially absorbed into the dispersion delay component of …

From The Circle To The Square: Symmetry And Degeneracy In Quantum Mechanics, Dahyeon Lee

Honors Papers

The relationship between degeneracy and symmetry in quantum mechanics is explored using two dimensional infinite potential wells with boundaries |x|^n + |y|^n = an for n = 2, whose limiting cases are circular (n = 2) and square (n ¿ 8) well. Analytic solutions for the circular and square cases are derived from separation of variables. Boundary element method (BEM) is a numerical method that solves PDEs using boundary conditions. The BEM is used to solve potential well problems. The method is first tested by comparing numerical solutions with analytic solutions for the circular and square wells. For the ground …

Reply To Comment On Origin Of Surface Canting Within Fe3o4 Nanoparticles, Kathryn L. Krycka, Julie A. Borchers, R.A. Booth, Yumi Ijiri, K. Hasz, J.J. Rhyne, S.A. Majetich

Faculty & Staff Scholarship

No abstract provided.

Particle Moment Canting In Cofe2o4 Nanoparticles, K. Hasz, Yumi Ijiri, Kathryn L. Krycka, Julie A. Borchers, R.A. Booth, S. Oberdick, S.A. Majetich

Faculty & Staff Scholarship

Polarization-analyzed small-angle neutron scattering methods are used to determine the spin morphology in high crystalline anisotropy, 11 nm diameter CoFe2O4 nanoparticle assemblies with randomly oriented easy axes. In moderate to high magnetic fields, the nanoparticles adopt a uniformly canted structure, rather than forming domains, shells, or other arrangements. The observed canting angles agree quantitatively with those predicted from an energy model dominated by Zeeman and anisotropy competition, with implications for the technological use of such nanoparticles.

Polarization Analyzed Small Angle Neutron Scattering Of Ferrite Nanoparticles, Kathryn Hasz

Honors Papers

Ferromagnetic nanoparticles offer a range of possible applications in nanotechnology, biomedical practices, and data storage, but important issues exist regarding their true magnetic structure. We have been investigating 9 nm diameter Fe3O4 nanoparticles and 11 nm diameter CoFe2O4 nanoparticles coated with an oleic acid shell. The nanoparticles were synthesized by solution chemistry methods and characterized by X-ray diffraction, SQUID, and vibrating sample magnetometry. Polarization Analyzed Small Angle Neutron Scattering (PASANS) was used under various temperatures and applied magnetic fields to investigate the magnetic structure of the particles. PASANS has revealed the iron oxide particles have a canted magnetic shell in …

The One Place We're Trying To Get To Is Just Where We Can't Get: Algebraic Speciality And Gravito-Electromagnetism In Bianchi Type Ix, Benjamin Kurt Lemberger

Honors Papers

Einstein's theory of General Relativity, put forward in 1915, predicts that space and time do not form a fixed background, but instead are malleable and dynamic quantities themselves. Their union forms something called spacetime, which when curved causes gravitational effects. This framework has led to models of the universe which match observations that the entire universe is expanding. Running these models backwards in time leads to a 'big bang', which is a single point from which the entire known universe came from. This single point is a singularity, a place where the theory breaks down, rendering questions like 'what happened …

Overtone Spectroscopy Of Hydrogen In Mof-5, Jocienne N. Nelson

Honors Papers

Metal-Organic Frameworks, or MOFs, are an exciting class of nanoporous crystalline materials with applications that include hydrogen storage and hydrogen isotope separation. The dynamics of adsorbed molecular hydrogen in the prototypical material known as MOF-5 have previously been studied using infrared spectroscopy. However, the rovibrational spectrum of the isotopologues, HD, and D2 were obscured due to overlap with the MOF peaks. Overtone infrared spectroscopy in conjunction with a diffuse reflectance geometry is used to observe the spectrum of H2, HD and D2. The overtone spectrum is shown to facilitate the identification of hydrogen peaks. Further, the spectrum of trapped H2 …

Inverted Linear Halbach Array For Separation Of Magnetic Nanoparticles, Chetan Poudel

Honors Papers

Magnetic nanoparticles have unique physical and chemical properties, making them appealing candidates for biomedical applications. These applications depend critically on size and magnetic uniformity of the nanoparticles. Unfortunately, very few purification methods exist to sort nanoparticles based on their magnetic properties. Here, we describe an unusual approach to this problem through our construction of a device containing a linear array of permanent magnets in a Halbach configuration, where successive magnet blocks have their magnetization orientation at right angles. The array provides a large region of relatively low magnetic field, yet high magnetic field gradient where sorting of nanoparticles based on …

Inverted Linear Halbach Array For Separation Of Magnetic Nanoparticles, Yumi Ijiri, Chetan Poudel, P. Stephen Williams, Lee R. Moore, Toru Orita, Maciej Zborowski

Faculty & Staff Scholarship

A linear array of Nd-Fe-B magnets has been designed and constructed in an inverted Halbach configuration for use in separating magnetic nanoparticles. The array provides a large region of relatively low magnetic field, yet high magnetic field gradient in agreement with finite element modeling calculations. The magnet assembly has been combined with a flow channel for magnetic nanoparticle suspensions, such that for an appropriate distance away from the assembly, nanoparticles of higher moment aggregate and accumulate against the channel wall, with lower moment nanoparticles flowing unaffected. The device is demonstrated for iron oxide nanoparticles with diameters of ~5 and 20 …

Doppler-Free Saturated Fluorescence Spectroscopy Of Lithium Using A Stabilized Frequency Comb, Michael E. Rowan

Honors Papers

The lineshapes of the D1 (22S1/2 → 22P1/2 ) and D2 (22S3/2 → 22P1/2) transitions in lithium were measured using a diode laser that was frequency-stabilized to a Ti:Sapphire 1 GHz optical frequency comb. The excitation was achieved by retroreflecting the diode laser, in effect producing the Doppler-free profiles for the center frequencies of transitions. The observed spectra were compared to density matrix calculations to gain insight into systematic effects including the dependence of Doppler-free profiles on power and polarization angle of the diode. For certain transitions, the method of saturated fluorescence spectroscopy inevitably leads to the presence of extra …

Velocity-Selective Direct Frequency-Comb Spectroscopy Of Atomic Vapors, Jason E. Stalnaker, S. L. Chen, M. E. Rowan, K. Nguyen, T. Pradhananga, C. A. Palm, Derek F. Jackson Kimball

Faculty & Staff Scholarship

We present an experimental and theoretical investigation of two-photon direct frequency-comb spectroscopy performed through velocity-selective excitation. In particular, we explore the effect of repetition rate on the [formula] two-photon transitions excited in a rubidium atomic vapor cell. The transitions occur via stepwise excitation through the [formula] states by use of the direct output of an optical frequency comb. Experiments were performed with two different frequency combs, one with a repetition rate of [formula] MHz and one with a repetition rate of [formula] MHz. The experimental spectra are compared to each other and to a theoretical model.

Polarization-Analyzed Small-Angle Neutron Scattering. Ii. Mathematical Angular Analysis, Kathryn L. Krycka, Julie A. Borchers, Yumi Ijiri, R.A. Booth, S.A. Majetich

Faculty & Staff Scholarship

Polarization-analyzed small-angle neutron scattering (SANS) is a powerful tool for the study of magnetic morphology with directional sensitivity. Building upon polarized scattering theory, this article presents simplified procedures for the reduction of longitudinally polarized SANS into terms of the three mutually orthogonal magnetic scattering contributions plus a structural contribution. Special emphasis is given to the treatment of anisotropic systems. The meaning and significance of scattering interferences between nuclear and magnetic scattering and between the scattering from magnetic moments projected onto distinct orthogonal axes are discussed in detail. Concise tables summarize the algorithms derived for the most commonly encountered conditions. These …

Model Of The One-Dimensional Molecular Hydrogen Cation, Joseph Galamba

Honors Papers

The hydrogen molecule ion is the simplest molecule, consisting of only two protons and an electron. As such, understanding this problem is essential in order to extend quantum mechanical techniques to more complex molecules such as the next simplest hydrogen molecule. The non-ionized hydrogen molecule represents the simplest system with only axial symmetry exhibiting Pauli exclusion principle effects due to the two identical electrons (fermions) in the neutral molecule. Both molecules have been treated in great detail both experimentally and theoretically and the nature of their solutions and energies are well understood.

Dimensional scaling of the problem can provide insight …

Two-Photon Direct Frequency Comb Spectroscopy Of Rubidium, Sophia Lee Chen

Honors Papers

Precision spectroscopy measurements have contributed significantly to our understanding of the fundamental structure of atoms. Here we present an experiment involving a new precision spectroscopic technique using a femtosecond optical frequency comb to excite two-photon transitions in rubidium. A femtosecond optical frequency comb is an ultrashort, pulsed laser with tens of thousands of frequencies, equally spaced in frequency-space. These frequencies can be used to excite atoms to specific transitions. The frequency comb is a versatile instrument that can avoid many of the experimental uncertainties that are associated with other spectroscopic techniques. The specific technique we use is called velocity selective …

Infrared Spectroscopy Of Trapped Gases In Metal-Organic Frameworks, Jennifer M. Schloss

Honors Papers

There are a range of environmental and industrial applications to capturing carbon dioxide from gas mixtures. Currently, materials being used in these applications bind carbon dioxide too strongly for practical purposes, such that they require large amounts of energy to be regenerated for reuse.

Highly porous materials called metal-organic frameworks (MOFs) could serve much more effectively as carbon-capturing materials, as they suck up large amounts of carbon dioxide gas at pressures and temperatures that are nearly ideal for carbon-capture applications. Moreover, they require much less energy than current materials to release the carbon dioxide and be regenerated. Additionally, many different …

Core-Shell Magnetic Morphology Of Structurally Uniform Magnetite Nanoparticles, Kathryn L. Krycka, R.A. Booth, C.R. Hogg, Y. Ijiri, Julie A. Borchers, W.C. Chen, S.M. Watson, M. Laver, T.R. Gentile, Liv R. Dedon

Faculty & Staff Scholarship

A new development in small-angle neutron scattering with polarization analysis allows us to directly extract the average spatial distributions of magnetic moments and their correlations with three-dimensional directional sensitivity in any magnetic field. Applied to a collection of spherical magnetite nanoparticles 9.0 nm in diameter, this enhanced method reveals uniformly canted, magnetically active shells in a nominally saturating field of 1.2 T. The shell thickness depends on temperature, and it disappears altogether when the external field is removed, confirming that these canted nanoparticle shells are magnetic, rather than structural, in origin.

Internal Magnetic Structure Of Magnetite Nanoparticles At Low Temperature, Kathryn L. Krycka, Julie A. Borchers, R.A. Booth, C.R. Hogg, Yumi Ijiri, W.C. Chen, S.M. Watson, M. Laver, T.R. Gentile, S. Harris

Faculty & Staff Scholarship

Small-angle neutron scattering with polarization analysis reveals that Fe3O4 nanoparticles with 90 Å diameters have ferrimagnetic moments significantly reduced from that of bulk Fe3O4 at 10 K, nominal saturation. Combined with previous results for an equivalent applied field at 200 K, a core-disordered shell picture of a spatially reduced ferrimagnetic core emerges, even well below the bulk blocking temperature. Zero-field cooling suggests that this magnetic morphology may be intrinsic to the nanoparticle, rather than field induced, at 10 K.

Infrared Spectroscopy Of H2 Trapped In Metal Organic Frameworks, Jesse Bennett Hopkins

Honors Papers

In this thesis we examine the hydrogen storage properties of four different materials. Because of the global climate crisis and the growing realization that petroleum resources are limited, there has been a strong push to find alternative means of energy storage. At the forefront of this push is the hydrogen economy, the idea that hydrogen gas is a bountiful, clean, alternative means of energy storage. One step towards realizing the hydrogen economy is finding a practical means of hydrogen storage.

The conventional methods of hydrogen storage are in high-pressure gas cylinders or as a liquid. Both of these methods are …

Radiative Transfer Models Of The Galactic Center, Everett A. Schlawin

Honors Papers

This thesis discusses research being done to understand the inner parts of the Milky Way Galaxy. We already know that there are dense star clouds, a supermassive black hole, and a large bar structure, but much of the inner galaxy is shrouded in mystery. Dust absorption, for one thing, prevents us from seeing the galactic center directly with our eyes.

To help understand the elusive inner Milky Way, we examine radio telescope data taken in Antarctica by Oberlin College Professor Chris Martin. His gigahertz radio observations were already analyzed to help understand how gas funnels into the Milky Way's supermassive …

Improving Pulsar Timing Through Interstellar Scatter Correction, Daniel Hemberger

Honors Papers

Though pulsar timing has confirmed the existence of gravitational waves, no technique has directly detected them. Jenet et al. state the requirements for the Parkes Pulsar Timing Array (PPTA) to make a significant detection of the stochastic gravitational wave background within five years. By employing the scintillation information in observations for each pulsar at every epoch, I believe interstellar scattering, an underestimated source of timing noise, can be corrected enough for the PPTA to meet these requirements. The improved detection threshold will help answer important questions about black hole mergers, galaxy evolution, and gravitation.

Low-Temperature Infrared Spectroscopy Of H2 In Solid C60, Hugh O.H. Churchill

Honors Papers

Diffuse reflectance infrared spectroscopy is used to measure the quantum dynamics of molecular hydrogentrapped within a C60 lattice at temperatures as low as 10 K. Crystal field effects in conjunction with rotational translational coupling lead to a rich spectrum with multiply split peaks that are more than an order of magnitude sharper than at room temperature. The induced redshifts in the vibrational-rotational mode frequencies are explained using a simple model in which the state dependence of the H2 polarizability leads to changes in the C60-H2 interaction potential.

The Quantum Dynamics Of H2 In A C60 Lattice, Christie Simmons

Honors Papers

Since its onset in 1941, matrix isolation has become a popular and common technique for studying species using spectroscopy by isolating them in an inert host solid [1]. Due to the large, spherical shape of the molecules, solid C60 has large interstitial voids making it a good host for matrix isolation. These voids come in two varieties. The larger of the two, the octahedral sites, have an ideal size for studying the dynamics of H2 molecules because the sites are large enough that a hydrogen molecule can be trapped, resulting in quantized translational motion, and can rotate nearly freely within …

Polar Measurements Of Mesospheric Co, Susannah Burrows

Honors Papers

An optically thin layer of carbon monoxide in the Earth's mesosphere results in strong, sharp emission peaks at CO's rotational transition frequencies. The J = 2 → 1 and J = 4 → 3 transitions were observed by the Antarctic Sub-millimeter Telescope / Remote Observatory (AST/RO), located at the Amundsen-Scott South Pole station. Mesospheric wind speeds were calculated from the Doppler shifts in emission spectra, as determined by least-squares fitting.